Understanding the biological mechanisms that underlie the anti-tumorigenic effects of calorie restriction and physical activity will likely be essential for translating laboratory advances in this field to the development of more effective strategies for preventing cancer in humans. The goal of Project 1 ofthe Penn TREC Survivor Center is to advance our understanding of the impact of energetics on breast cancer recurrence. Project 1 will use an innovative genetically engineered mouse model for breast cancer recurrence developed at Penn to determine the effects of exercise, calorie restriction, or their combination on breast cancer recurrence. Mammary tumors will be induced in oven/veight mice by the doxycycline-dependent activation of an oncogene relevant to human breast cancer in the mammary glands of mice fed a high fat diet. Regression of the resulting tumors will be induced by oncogene down-regulation to generate cohorts of mice bearing dormant residual tumor cells. Overweight mice bearing residual disease will be randomly assigned to exercise, calorie restriction, both of these interventions, or neither and followed for cancer recurrence. Biomarkers will be evaluated to explore the hypothesized relationship between energy balance and recurrence and will include markers reflecting the PI3K-Akt-mT0R pathway, insulin resistance, IGF-1, HGF, adipokines, inflammation, tumor angiogenesis and oxidative stress. To our knowledge, this study will be the first to explore the impact of exercise and calorie restriction on cancer recurrence in an animal model. The studies proposed in Project 1 build on the unique combination of strengths and expertise in cancer biology, obesity, endocrinology, and exercise physiology among researchers in the proposed Penn TREC Survivor Center. In addition, the design of this study closely parallels an analogous human trial proposed in Project 2. The assembled team of investigators will work jointly to create new experimental paradigms that integrate and move beyond discipline-specific approaches to address the role of energy balance in breast cancer recurrence. In doing so, this project will advance the mission ofthe Penn TREC Survivor center to promote transdisciplinary, translational science on energy balance and cancer survivorship.